(a) Field of the Invention
The present invention relates to a method and an apparatus capable of easily and accurately measuring the floating amount or static behaviors of floating motion such as pitch angle and balance as well as dynamic behaviors such as floating and frequency fluctuations of the magnetic head, particularly of the gimbal type which is intended to use with the magnetic disk, which can excellently follow up the movement of the magnetic disk, and which is allowed to have small head pressure. The present invention also relates to a method and an apparatus for enabling these measurements to be achieved even when the floating amount of the magnetic head is extremely low.
(b) Prior Art
The floating amount of the magnetic head was conventionally measured relating to mainly its floating motion or static behaviors such as pitch angle and balance wherein white light was used as the light source and color phase changes in interference fringes caused in a space between the rotating glass disk and that face of the magnetic head which was opposite to the glass disk were discriminated by eyes or wherein a single color light was used and calculation was made on the basis of the strength of interference fringes on that face of the magnetic head which was opposite to the glass disk.
A typical example of these conventional techniques will be described referring to FIG. 1. FIG. 1 is a block diagram showing one of the conventional measuring apparatuses. In FIG. 1, numeral 1 represents a magnetic head supported by a gimbal 2. Numeral 3 denotes a monochromatic light source and monochromatic beam emitted from this laser light source 3 is reflected by a beam splitter 4 in a direction substantially perpendicular to the monochromatic beam incident upon the beam splitter 4. Passing through a glass disk 5 which is horizontally rotated between the beam splitter 4 and the magnetic head 1, the monochromatic beam reflected by the beam splitter 4 is cast to an optional point on that face of the magnetic head 1 which is opposite to the glass disk 5. The glass disk 5 is made of quartz which is stable in optical property, and numeral 6 represents a drive motor for driving the glass disk 5.
When the monochromatic beam is cast like this onto that face of the magnetic head 1 which is opposite to the glass disk 5, passing through the glass disk 5, interference fringes are generated in a space between the glass disk 5 and that face of the magnetic head 1 which faces the glass disk 5. The interference fringes are photoelectrically converted by a photoelectric converter element 7 such as the photosensor and calculated by a computer section 9 through an A/D converter section 8, so that the floating amount of the magnetic head at the one optional point can be measured along with floating fluctuations caused by vibration and the like. In FIG. 1, numeral 21 denotes a beam expander, 22 an objective and 23 an imaging lens.
In the conventional case as described above and shown in FIG. 1, however, the measurement of pitch angle and balance of the magnetic head made it necessary to drive the whole of the optical system and move the monochromatic beam spot. This was a troublesome operation and it was also difficult to move the monochromatic beam spot at high speed. In the case where the measurement was made, using white light and seeing color phase changes in interference fringes, the floating amount which was extremely low or less than the visible light could not be measured.